I wonder if there's a possibilty of Saturn emulation on Rev. I remember rumors of a Sat emu for DC, but of course nothing ever came of them. However, it seemed like Sega might have at least considered the possibility. Perhaps there's some code laying around.
As for Rev's emulation quality, I suspect that it'll be good enough for most but crappy for the console "purists" out there.
It sounds like it'll all be software based, so it should be possible to upgrade the emus for better compatibility if necessary.
Now, if Nintendo announces their next Gameboy with virtual console capability/compatibility with Rev, then they will have become the Apple/iTunes/iPod of video games.